Electronic equipment units, such as magazine racks or sub-racks of telecommunications cabinets, frequently include stacked plug-in units in the form of printed circuit boards (PCB) or cards. Such multiple plug-in units are normally densely stacked in order to effectively use the available space within the magazine rack. A common requirement is that it must be possible to replace plug-in units in a magazine rack without disturbing other units therein. The replacement may also have to be performed with the power to the magazine on.
Dense stacking may cause problems in connection with such replacement of plug-in units, when plug-in units are inserted into, and to a certain degree also when they are withdrawn from, a magazine rack. In particular, problems appear before the plug-in units enter and are properly guided in associated top and bottom edge guide channels. Due to inappropriate or careless replacement of plug-in units neighbouring plug-in units may easily be damaged by components or connectors associated with the replaced units. Altogether, this may cause problems that are especially severe in situations where adjacent units in a magazine stack must be maintained in operating mode during replacement of a unit. Inadvertent contact between plug-in units of a magazine may have various consequences, ranging from simple scratching or scraping of components and/or circuitry of a printed circuit board and to very severe short circuiting of an entire plug-in unit.
No attempts to solve the discussed types of problems have been noted in the prior art. In related areas attempts have been made to solve problems associated especially with replacing expansion cards in live computer chassis. Solutions presented for use in such environments involve the use of special plastic material carriers that accommodate, guide and protect the expansion cards. Apart from being expensive such enclosing card carriers would require unacceptably much space in a magazine.